Artificial line



Oct. 30, 1928.

R. FELDTKELLER y ARTIFICIAL LINE Filed March 51, 1926 ffy | l l 0 2000 4000 6000 w00 (0000 |2000 |4000 o Zoo 4000 sooo nooo loooo lzooor be Patented Oct.v 30, 19.28.

RICHARD FELDTKELLER, OF CHARLTTENBURG, GERMANY. ASSIGNOR TO SIEMENS &

HALSKE AKTIENGESELLSCHAFT, 0F SIEMENSSTADT,

PANY OF GERMANY.

BERLIN, GERMANY, A 00M- ARTIFIGIAL LINE.

Appli-cation led March 31, 1926, Serial No. 98,642, and in Germany December 9, 1924.

This invention relates to artificial lines for balancing loaded telephone lines and is an improvement in the artificial lme described and claimed in the Patent No. 1,647,985 granted to Valter Deutschmann, on November 8. 1927.

Theapplication referred to above describes a simulation of the impedance of loaded lines by means of a symmetrical network correspondingto one link of the llne, the network having the same iterative impedance as the line, the cut-off frequency, however, being higher than that of the l1ne and the network being closed by an ohmic resistance.`

The present invention includes a further development of this simulation. According to the invention the network has an unsymmetrical construction, by means of which. t

e imaginary part of the iterative impedance of the cable is better simulated for the Ihigher speech frequencies. The simulation of which depend on the frequency in almost..

the same manner as those of the cable.

The underlying principle of the invention is .explained by the embodiment of the invention illustrated in Fig. 1 and the graphs of Figs. 2 and 3. In Fig. 1 the network consists of the coil L, the ohmic resistance 1' and the condensers C1 and C2 which are 0f different size according to the invention. The terminal of the network is closed by magnitude in which Lk and Ck signify the induction and capacity of the cable. The quantity expressedby the above formula is the value of the characteristic impedanceof the line at low frequencies and is known as the nominal characteristic impedance. The condenser C,

the' ohmic resistance R, of the.

is connected to the line in front of the network. Fig. 2 illustrates the real and imaginary'part of the iterative impedances of the ,i

cable andvarious simulations as a function of the frequency. The curves 1 represent the cable, curves 2 a simulation in which C1 `tion is entirely in the positive range. Curve 3, for an unsymmetrical connection, Shows negative values for higher frequencies, and

by connecting the condenser-Co'the simulation will have a negative. reactance, which can also easily be adjusted to that of the cable in the low frequency range as seen from curve 4.

The variations of the magnitude ofthe imaginary part for higher frequencies in general present no disadvantage in practice, but on the contrary, a great advantage. When in operation the cable is terminated by a ring-translator and ringing current blocking condensers. The initial resistance v is thereby changed in such a manner that its imaginarycomponents assure high negative values for the entire .speech frequency range, whereas the real -part is changed very slightly.l According to the invention the unbalance of the network and the longitudinal condenser Co can be selected in such a manner that a simulation is obtained without making it necessary to simulatethe ringtranslator and the ringing current blocking condensers in thex same way. The curves,l

representing this case are plotted in Fig. 3. The numerals of the separate curves have the same significance as in Fi .'2. Fig. 3 shows that an excellent simulation can be constructed in this case. l

When the repeater sections are too short,

it is'desirable to connect an artificial eXten`- sion to the cable, whichreduces itsl attenual 1 I tion to the value of the normal.. repeater section without noticeably changing the`- y initial resistance. It is most suitable to :con-

nect it between the ring-translator and repeuter, and it will inuence the real part only in the higher frequencies. Also in this case'the simulations constructed according to the invention can be applied without making it necessar to simulate the ring-translator, the bloc ing condensers and the extension line by simular elements.

What is claimed is:

l. A11 impedance network for simulating the 'impedance of the long coil-loaded line, comprising an unsymmetrical II type network corresponding in form to one section of the line to be simuladed, and having aproximately the same nominal characteristic impedance, but being proportioned in accordance with a higher cut-ofi'. frequency than that of the line,v and an ohmic resistance connected to two terminals of said network, said ohmic resistance having a value substantially equal to the nominal characteristic impedance of the line.

2. A balancing network in accordance with claim 1, and a condenser in series therewith' whereby the combination is adapted to simul late more closely the impedance -of the line at low frequencies.

In witness whereof, I hereunto subscribe my name this 1st day of March A. D., 1926.

RICHARD FELDTKELLER. 

